Maria Mikulska was a nun in a Benedictine convent in Wilna (now Vilnius, Lithuania). When German troops occupied the city in June 1941, violence against the population increased. Jews were persecuted and incarcerated in a ghetto. In the fall of 1941, the Jewish Bak and Schapiro families sought refuge in the Catholic convent. Maria Mikulska took care of the five of them in hiding. At the end of 1941, the Wehrmacht requisitioned the convent and set up an archive in the building. Mikulska was arrested, along with other nuns, and later put into a labor camp.
After her release, Mikulska worked as a cleaner in the former convent. Father Juozas Stakauskas set up a hiding place in the building, which housed nine Jewish people. In 1943 Mikulska advocated for Mitzia and Samuel Bak to be taken in there as well. She provided the people in hiding with food and medications, and kept them informed of the course of the war.
The hiding place was destroyed by grenades in July 1944, shortly before the German retreat from Wilna. The people inside survived. In 1974 Maria Mikulska was honored as Righteous Among the Nations.